In 2373, upon learning that Kes had been uncontrollably traveling back in time from the moment of her death, The Doctor and LieutenantTorres began a procedure to irradiate Kes with a modulated field of antichronitons to purge her system of the chroniton radiation to which she had been exposed in a future time period, and which, in combination with a biotemporal field to which the The Doctor had exposed her in the future, placed her in a state of biotemporal flux, causing her time jumps. Placing Kes in a bio-temporal chamber and initiating the antichroniton field, Kes experienced a series of more time jumps as far back as her own conception, at which point she returned to the present, and was brought back into temporal sync. (VOY: "Before and After")